Surgical hand tools of electrically powered type have long been known. Reusable tools of this type must be sterilized prior to surgical use on each new patient. Particularly effective sterilization can be obtained by exposing the hand tool to high temperature steam for a period of time.
However, in electrically powered tools of this type, the repeated application of high temperature and humidity, due to recurring placement in a steam autoclave or the like, has damaged electrical motors of the type having a rotating armature surrounded by permanent magnets adhesively bonded to the interior surface of the surrounding motor casing. The adhesive bonding is typically done by an epoxy or related resin. At room temperature and moderate humidity levels, such bond strongly and reliably holds the magnets in place within the casing. However, it has been found that the high temperature and humidity environment encountered in sterilizing the tool tends to degrade such adhesive bond, such that magnets have become loose within their casings and have rendered their respective motors inoperative, thereby rendering the corresponding surgical tool inoperative.
Further in permanent magnet motors of this kind, even if not to be subjected to high moisture and temperature conditions, permanent affixing of the magnets in the casing by adhesive bonding has the further disadvantages of being time consuming, relatively expensive, subject to error in location and being subject to unreliability if bonding conditions are not precisely controlled (e.g. if surfaces are not clean, temperature is out of range, etc.).
Accordingly, the objects and purposes of this invention include provision of apparatus directed to overcoming the aforementioned problems in prior art devices.